<h2>AAS 95-443</h2><h2>Tracking and Data Relay Satellite System (TDRSS) Support of User Spacecraft Without TDRSS Transponders</h2><h4>J. Jackson and G. C. Marr, NASA Goddard Space Flight Center,Greenbelt, MD, M. Maher, Allied Signal Technical Services Corp.</h4><h2> Abstract </h2>NASA GSFC VNS TSG personnel have proposed the use of TDRSS to obtain telemetry and/or S-band one-way return Doppler tracking data for spacecraft which do not have TDRSS-compatible transponders and therefore were never considered candidates for TDRSS support.  For spacecraft with less stable local oscillators (LOs), one-way return Doppler tracking data is typically of poor quality.  It has been demonstrated using UARS, WIND, and NOAA-J tracking data that the simultaneous use of two TDRSS spacecraft can yield differenced one-way return Doppler data of high quality which is usable for orbit determination by differencing away the effects of oscillator instability.
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